The Ecological Dynamics of Fecal Contamination and Salmonella Typhi and Salmonella Paratyphi A in Municipal Kathmandu Drinking Water
Open Access
- 6 January 2016
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Neglected Tropical Diseases
- Vol. 10 (1), e0004346
- https://doi.org/10.1371/journal.pntd.0004346
Abstract
One of the UN sustainable development goals is to achieve universal access to safe and affordable drinking water by 2030. It is locations like Kathmandu, Nepal, a densely populated city in South Asia with endemic typhoid fever, where this goal is most pertinent. Aiming to understand the public health implications of water quality in Kathmandu we subjected weekly water samples from 10 sources for one year to a range of chemical and bacteriological analyses. We additionally aimed to detect the etiological agents of typhoid fever and longitudinally assess microbial diversity by 16S rRNA gene surveying. We found that the majority of water sources exhibited chemical and bacterial contamination exceeding WHO guidelines. Further analysis of the chemical and bacterial data indicated site-specific pollution, symptomatic of highly localized fecal contamination. Rainfall was found to be a key driver of this fecal contamination, correlating with nitrates and evidence of S. Typhi and S. Paratyphi A, for which DNA was detectable in 333 (77%) and 303 (70%) of 432 water samples, respectively. 16S rRNA gene surveying outlined a spectrum of fecal bacteria in the contaminated water, forming complex communities again displaying location-specific temporal signatures. Our data signify that the municipal water in Kathmandu is a predominant vehicle for the transmission of S. Typhi and S. Paratyphi A. This study represents the first extensive spatiotemporal investigation of water pollution in an endemic typhoid fever setting and implicates highly localized human waste as the major contributor to poor water quality in the Kathmandu Valley. Aiming to understand the ecology of municipal drinking water and measure the potential exposure to pathogens that cause typhoid fever (Salmonella Typhi and Salmonella Paratyphi A) in Kathmandu, Nepal, we collected water samples from 10 water sources weekly for one year and subjected them to comprehensive chemical, bacteriological and molecular analyses. We found that Kathmandu drinking water exhibits longitudinal fecal contamination in excess of WHO guidelines. The chemical composition of water indicated site-specific pollution profiles, which were likely driven by localized contamination with human fecal material. We additionally found that Salmonella Typhi and Salmonella Paratyphi A could be detected throughout the year in every water sampling location, but specifically peaked after the monsoons. A microbiota analysis (a method for studying bacterial diversity in biological samples) revealed the water to be contaminated by complex populations of fecal bacteria, which again exhibited a unique profile by both location and time. This study shows that Salmonella Typhi and Salmonella Paratyphi A can be longitudinally detected in drinking water in Kathmandu and represents the first major investigation of the spatiotemporal dynamics of drinking water pollution in an endemic typhoid setting.Keywords
This publication has 36 references indexed in Scilit:
- Patent Human Infections with the Whipworm, Trichuris trichiura, Are Not Associated with Alterations in the Faecal MicrobiotaPLOS ONE, 2013
- Differential Epidemiology of Salmonella Typhi and Paratyphi A in Kathmandu, Nepal: A Matched Case Control Investigation in a Highly Endemic Enteric Fever SettingPLoS Neglected Tropical Diseases, 2013
- Impact of vehicular strike on particulate matter air quality: Results from a natural intervention study in Kathmandu valleyEnvironmental Research, 2013
- Combined high-resolution genotyping and geospatial analysis reveals modes of endemic urban typhoid fever transmissionOpen Biology, 2011
- The Burden and Characteristics of Enteric Fever at a Healthcare Facility in a Densely Populated Area of KathmanduPLOS ONE, 2010
- Ground water quality in the Kathmandu valley of NepalEnvironmental Monitoring and Assessment, 2010
- The sensitivity of real-time PCR amplification targeting invasive Salmonellaserovars in biological specimensBMC Infectious Diseases, 2010
- Discriminant analysis of principal components: a new method for the analysis of genetically structured populationsBMC Genetics, 2010
- Bacterial Community Composition of Stream Biofilms in Spatially Variable-Flow EnvironmentsApplied and Environmental Microbiology, 2009
- adegenet: a R package for the multivariate analysis of genetic markersBioinformatics, 2008